Might be because you used/transfered your 3GS backup onto your new iphone 4.
I'd restore and setup as new phone. You should notice a big improvement.
Also its good to restart the phone once in a while.

Yes, I think I did do that. How do I do this but get my contacts, emails, and apps the way I want them?

You can sync your contacts to your computer and then copy them back using itunes. Same thing with your apps, they're all there on your library.
Your emails, texts and any game progress will be gone though.
Up to you.

You can sync your contacts to your computer and then copy them back using itunes. Same thing with your apps, they're all there on your library.
Your emails, texts and any game progress will be gone though.
Up to you.

So if I do this what exactly am I getting rid of? Is it just all the old junk that came over from the 3Gs? I'm confused.

So if I do this what exactly am I getting rid of? Is it just all the old junk that came over from the 3Gs? I'm confused.

Yes, you're setting it up as a new phone.
All the stuff and configuration from your 3GS wont transfer over to the new iphone 4 and bugs and issues that could copy from old backups will be eliminated.
Give it a try, your backup is still there so you if you feel the need to restore from backup at a later time you have the option.
But I personally like to setup as new phone even after firmware updates.

just make sure you go through and sync the phone with Outlook or a similar program to save all your contacts, notes, etc. You have to click those options in the Info section of iTunes. Also save your pictures.

If you do it all right, you wonlt lose much. As mentioned, just your text messages and user data. Meaning High scores on angry birds will be gone, stuff like that.

just make sure you go through and sync the phone with Outlook or a similar program to save all your contacts, notes, etc. You have to click those options in the Info section of iTunes. Also save your pictures.

If you do it all right, you wonlt lose much. As mentioned, just your text messages and user data. Meaning High scores on angry birds will be gone, stuff like that.

Well I have Mobile Me so all my contacts, bookmarks, etc. should be easy to get back on the phone after I restore.